colosseum
Originally the Flavian Amphitheatre, an elliptical amphitheatre in the centre of the city of Rome, Italy, the largest ever built in the Roman Empire, built of concrete and stone. It is considered one of the greatest works of Roman architecture and Roman engineering and is also famous as a gladiatorial arena. The name is derived from the Colossus of Rhodes, a giant statue of Apollo which stood near (but not inside) the Amphitheatre.
Note that this tag is not limited to the real life colosseum, as it also includes fantastical depictions of an arena inspired after the real life arena.